 The Set Path Group ID command, with the dynamic path selection (DPS)
function, provides greater flexibility in operations on reserved devices.Once a path group for a device has been established, it may be accessed
over any path which is a member of the group to which it is reserved.In
addition, on 370-XA systems which set the multipath mode bit in the
function control byte (byte 0) to a 1, block multiplex reconnections will
occur on the first available path which is a member of the group over which
the channel program was initiated (regardless of the reservation state of the
device).